What is an ignition interlock device and when is it required?

What the Law Says

California law mandates installation of an ignition interlock device (IID) following any conviction for driving under the influence (DUI), regardless of whether it’s a first, second, or subsequent offense. The requirement applies statewide under a pilot program expanded to all counties in 2019.

An IID is a breathalyzer wired to a vehicle’s ignition system. Before starting the car, the driver must blow into the device; if alcohol above a preset limit (typically 0.02% BAC) is detected, the engine will not start. The device also requires random ‘rolling retests’ while driving to prevent circumvention.

The length of the required IID installation depends on the number of prior DUI convictions within the past 10 years: 6 months for a first offense, 1 year for a second, 2 years for a third, and 3 years for a fourth or subsequent offense.

The IID requirement applies to all drivers convicted of VC § 23152 (DUI) or § 23153 (DUI causing injury), and begins immediately upon license reinstatement — not at the time of conviction or sentencing.

Statutory Text

For a first violation of Section 23152 or 23153, the court shall order the installation of an ignition interlock device for a period of six months.

— Vehicle Code § 23575.5(a)(1) — Mandatory IID for First Offense

Statutory Text

For a second or subsequent violation… the court shall order the installation… for a period of one year for a second violation, two years for a third violation, and three years for a fourth or subsequent violation.

— Vehicle Code § 23575.5(a)(2)–(4) — IID Duration for Repeat Offenses

Statutory Text

The pilot program… is expanded to include all counties in the state, effective January 1, 2019.

— Vehicle Code § 23575.7(b) — Statewide IID Program

Sources